Energy Storage for Hybrid Military Vehicles

Monday, 01 October 2007

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In this connection, the thermal runaway (TR) phenomenon has been often observed in sealed cell designs and this raises a potential problem in battery applications incorporating sealed batteries. As a practical matter, sealed batteries are preferred over the classical flooded designs. It is not efficient to design around the worstcase scenario, i.e., anticipating the thermal runaway effect. It is wiser to detect its onset and shut down the charging process. An alternative approach is to develop an understanding of the TR process and perhaps develop a method for effectively controlling or eliminating it altogether.

In the case of lithium batteries, the thermal runaway effect is compounded by the potential for inducing the oxidation of the electrolyte solvent. A number of alternatives are being considered to minimize or eliminate this potential failure mode. This particular problem is not considered to be significant in the smaller lithium ion cells. However, the larger cells have a mass-to-surface area ratio that limits the rate of heat transfer. The consequence of this is that during heat generation, higher internal temperatures are developed to dissipate the heat produced. This heat rejection issue is a matter of ongoing investigation.